Temperature-actuated valve assembles that open or close at a predetermined temperature are used in a wide variety of industries. In the avionics industry, temperature-actuated valve assemblies are commonly used as over-temperature shutoff valves in airplane bleed air systems. Such over-temperature shutoff valves are configured to close to thereby protect temperature sensitive downstream components, when fluid conducted by the valve assembly becomes too hot. Some over-temperature shutoff valves of this type employ thermal fuse plugs made of eutectic alloys that abruptly melt at a predetermined actuation temperature. The fuse plug maintains a spring-loaded flapper or other such valve element in an open position. When the bleed air heats the fuse plug to its melting point, the fuse plug abruptly melts and the flapper or valve element is permitted to swing shut.
Even though over-temperature shutoff valves of the type described above are effective for decreasing airflow in an airplane when the bleed air surpasses a particular temperature threshold, the fuse plugs employed by such shutoff valves require replacement after each valve actuation. Although over-temperature shutoff valves have been developed that employ non-perishable temperature sensitive components, such over-temperature shutoff valves may still require manual intervention to be reset. As such, such over-temperature shutoff valves are not readily lent to applications in other industries.
In many industries, such as the power industry, there is a need to regulate fluid flow dynamically in response to plant load and/or varying process requirements. Such varying fluid flow can be facilitated via a control valve replete with pneumatic or motor operated actuation, provided a robust control system is implemented. The dynamic function of such a control valve is desirable in that operation of the control valve can be programmed or specified to meet specific plant operating nuances in order to optimize plant performance and efficiency. However, achieving such dynamic function using a control valve and control system comes at the cost of increased control complexity, increased number of moving parts, increased equipment wear, and decreased operational reliability.
Considering the foregoing, it is desirable to provide a reliable, temperature-actuated valve assembly with relatively few components configured to actuate to allow fluid flow or to increase fluid flow upon a fluid reaching a predetermined temperature or increasing in temperature beyond a predetermined temperature. It would also be desirable if such a valve assembly were configured to automatically reset to prevent flow or to decrease fluid flow upon a fluid reaching a predetermined temperature or decreasing in temperature beyond a predetermined temperature.